The present invention relates to a semiconductor device having a ferroelectric substance capacitor, particularly to a structure for high integration.
As high integration and michronization of semiconductor device advance, an occupying area of each part is decreased largely in LSI, and research or providing as semiconductor mall and high in reliability is repeated.
In the semiconductor device having the ferroelectric substance capacitor being researched now, a capacitor using an ordinary insulating layer for dielectric substance layer such as a capacitor, called PIP capacitor, having an insulating layer between polysilicon layers, or a capacitor, called MOS capacitor, formed sandwiching a silicon oxide film between a silicon layer and metal is used greatly at the same time in order to detect reverse charge quantity of the ferroelectric substance capacitor and to convert to voltage.
That is, a ferroelectric substance capacitor CFERO and PIP capacitor CPIP are used greatly in series connection as shown in the equivalent circuit of FIG. 7.
Conventionally, in order to realize such the semiconductor device, as shown in FIGS. 8A and 8B, a first capacitor is formed on an element separating insulating film 2 formed on surface of a silicon substrate 1 and a second capacitor of a ferroelectric substance capacitor is formed so as to line with the first capacitor on the upper layer of the element region surrounded by the element separating insulating film 2. The first capacitor and the second capacitor are connected in series through a wiring pattern connected mutually through contact holes.
Here, the first capacitor is constructed by a first electrode 3 of a polysilicon layer formed on the element separating insulating film 2, a first insulating film 4 formed as two layers of a silicon oxide layer and a silicon nitride layer on the upper layer thereof, and a second electrode 5 of a polysilicon layer formed further the upper layer thereof.
The second capacitor is formed on the upper layer of the element region surrounded by the element separating insulating film as a not-common capacity, and the second capacitor includes a first electrode 7, a ferroelectric substance film 8, and a second electrode 9.
The mutual connection of the first and second capacitors is achieved through a wiring pattern 10 connected through contact holes.
Such the capacitor structure has large occupying area and it has been a large problem preventing michronization in LSI.
Further, there has been a problem that an escape route of noise is few so as to receive easily influence of noise as a device as shown in a explanation view of FIG. 9.
Thus, the conventional semiconductor device including the ferroelectric substance capacitor has large occupying area and it has been a large problem to prevent high integration of the device.
Further, the device easily receives influence of noise and it causes malfunction.
The invention is performed in view of the circumstances, and an object of the invention is to provide a semiconductor device having a ferroelectric substance capacitor small in the occupying area and large in capacitance.
An another object of the invention is to provide a semiconductor device having a ferroelectric substance capacitor reducing influence of noise and being few in malfunctions.
The invention is characterized by including a first capacitor formed on surface of a semiconductor substrate and a second capacitor of a ferroelectric substance capacitance laminated on the first capacitor so as to connect in series.
According to such the construction, it is possible to reduce occupying area without reducing capacitance because the first capacitor and the second capacitor of the ferroelectric substance capacitor are stacked. Since long wiring is reduced in the semiconductor device, propagation of noise is reduced and it is possible to reduce malfunction.
Preferably, the invention is characterized by that the first capacitor is formed on an element separating insulating film.
According to such the construction, it is possible to use efficiently on the element separating insulating film because the first and second capacitors are formed on the element separating insulating film. Since the capacitors are formed on the thick element separating insulating film, it is possible to provide high LSI in reliability at michronization without the element region in the substrate does not receive bad reflection even at possible diffusion such as Pb or O2 from the ferroelectric substance thin film.
Preferably, the invention is characterized by that the upper electrode of the first capacitor and the lower electrode of the second capacitor are connected through plugs formed at an interlayer insulating film.
According to such the construction, the capacitor is high in reliability because the capacitor of laminating structure is formed using well a process for forming another element region.
Since the ferroelectric substance thin film or the ferroelectric substance capacitor and the electrode of the first capacitor are connected through plugs without contacting directly, diffusion such as Pb or O2 from the ferroelectric substance thin film is cut off well only forming a barrier layer on the plug.
Preferably, the invention is characterized by connecting the upper electrode of the first capacitor and the lower electrode of the second capacitor are connected through a wiring layer formed on the upper layer or the second capacitor.
According to such the construction too, it is possible to obtain a laminating layer capacitor including good series connecting body.
Preferably, the invention is characterized in that the upper electrode of the first capacitor and the lower electrode of the second capacitor have a common electrode, and that a capacitor insulating film for the first capacitor is arranged at the lower layer side of the common electrode and the ferroelectric substance film is arranged at upper layer side.
According to Such the construction, since the upper electrode of the first capacitor and the lower electrode of the second capacitor have a common electrode, forming of the electrode layer and the interlayer insulating film is needless, and it is possible to provide a semiconductor device very simple and a little in difference of surface level.
In the case using such the structure, although diffusion such as Pb or O2 from the ferroelectric substance thin film becomes a problem, by using high material in oxygen shielding effect such as two layers structure film of iridium and iridium oxide as the common electrode, diffusion such as Pb or O2 from the ferroelectric substance thin film is depressed well, and it is possible to provide high device in reliability.
By adopting such the construction, floating capacitance removes and it is possible to design high driving speed.
Preferably, the invention is characterized in that the lower electrode of the second capacitor includes the laminating film of iridium and iridium oxide.
According to such the construction, diffusion such as Pb or O2 from the ferroelectric substance thin film is depressed well, and it is possible to provide high device in reliability.